Adjusting arrangement for a fluidised bed device

ABSTRACT

In a fluidised bed device having a perforated channel for a stream of material travelling through said channel, and a chute for the outflow of said stream out of said channel, the arrangement that the bottom of said chute follows said channel in prolongation of the bottom of said channel, said chute forming a free outlet for said stream, and that a regulating means is provided capable of varying the friction between said stream and said bottom of said chute.

United States Patent [1 1 Biaggi et a1.

[451 Apr. 23, 1974 ADJUSTING ARRANGEMENT FOR A FLUIDISED BED DEVICE [75] Inventors: Jacques Biaggi, Ville diAvray,

France; Jakob Oertle, Winterthur, Switzerland; Michael Leonhardt, Aichach Post Weiler, Germany [73] Assignee: Escher Wyss Limited, Zurich,

Switzerland 22 Filed: July 25,1972 21 Appl. N01: 275,054

[30] Foreign Application Priority Data July 26, 1971 France 71.27258 [52] US. Cl. 34/57 R, 302/29 [51] Int. Cl. F26b 17/10 [58] Field of Search 34/57 A, 57 C, 57 R, 10;

[56] References Cited UNITED STATES PATENTS 3,304,619 2/1967 Futer 34/10 3,543,414 12/1970 Gomarin 34/57 A X 2,513,369 7/1950 Shaw 34/10 3,188,144 6/1965 Gmur et a1 302/29 FOREIGN PATENTS OR APPLICATIONS 1,058,084 2/1967 Great Britain 34/57 R 545,532 8/1957 Canada 302/29 Primary ExaminerWilliam E. Wayner Assistant ExaminerWilliam C. Anderson Attorney, Agent, or Firm-Autin P. Dodge; Robert A. Ostmann [57] ABSTRACT In a fluidised bed device having a perforated channel for a stream of material travelling through said channel, and a chute for the outflow of said stream out of said channel, the arrangement that the bottom of said chute follows said channel in prolongation of the bottom of said channel, said chute forming a free outlet for said stream, and that a regulating means is provided capable of varying the friction between said stream and said bottom of said chute.

9 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION The invention relates to regulating the height of a fluidised bed of a stream of material travelling through a perforated channel of a fluidised bed device which comprises a chute for the outflow of the stream of material.

In many cases a stream of powder, granular or crystalised solids is conveyed in the form ofa fluidised bed. For this purpose a stream of such material particles is sent through a channel the bottom of which consists of a perforated plate below which is arranged a box into which air or gas can be admitted. The air entering the channel from this box forms with the material particles a fluidised bed travelling over the bottom of the channel. This method is particularly advantageous for various processes dealing with these particles, for example when treating them in a so-called fluidised bed drier. By conveying the material in the form of a fluidised bed, with this drier a better drying effect is obtained.

It is known to arrange at the outlet of the channel obstacles which are situated in the path of the outflowing stream of material, in order to .keep the height of the fluidised bed to a desired value. In known fluidised bed devices, displaceable gates or pivotable flaps are used for this purpose. These regulating means, however, have the disadvantage of blocking the outflow from the perforated channel by forming lumps from the material particles. In order to avoid such disturbances, fluidised bed devices provided with such regulating means hav to be continually supervised.

SUMMARY OF THE INVENTION The invention has as its object an arrangement by means of which the desired height for the fluidised bed of a fluidised bed device can be regulated automatically, that is to say without blockages having to be eliminated from time to time.

This object is achieved in the device described initiallyaccording to the invention in that'the bottom of said chute follows said channel in prolongation of the bottom of said channel, that said chute forms a free outlet for said stream of material, and that a regulating means is provided capable of varying the friction between said stream and the bottom of said chute.

In a particularly advantageous embodiment of the invention, the bottom of the chute has perforations and comprises underneath it an air supply box for passing a variable flow of air through the perforations of said bottom.

For varying said flow of air passing through, it is advantageous to make the air supply box capable of being supplied with air at variable pressure. Likewise, the size of the perforations in the bottom of the chute can be made variable. Or, to vary said flow of air, a shield can be provided which is slidable along the bottom of the chute.

The friction between the stream of material and the bottom of the chute can advantageously be varied also by sub-dividing the bottom of the chute into at least two portions, in the direction of movement of said stream, the portion which is downstream in the direction of movement of said stream being telescopically 2 displaceable relatively to the preceding portion, so that the length of the chute can be varied.

In all described embodiments it may be advantageous to have the bottom of the chute inclined in the direction of movement of said stream at least locally relatively to the horizontal.

Furthermore, the friction which occurs between the stream of material and the bottom of the chute can advantageously be made variable by making the inclination of the bottom of the chute variable. This is particularly advantageous in the case of a non-perforated chute bottom, i.e. in a construction without an air supply box. The entire chute can be inclined, for which purpose there is provided between the bottom of the channel and the bottom of the chute a hinge, or a portion of the chute bottom can be secured by means of a hinge on the portion of the chute bottom which precedes it in the direction of movement of the stream of material.

BRIEF DESCRIPTION OF THE DRAWING Embodiments of the invention are shown in simplifled manner in the drawing by means of which the invention will be explained in detail.

FIG. 1 shows a side view partly in section of a fluidised bed drier provided with the arrangement according to the invention,

FIG. 2 shows a view of a fragment of FIG. 1 on a larger scale,

FIGS. 3 to 5 show vertical sections corresponding to FIG. 2 through further embodiments, and

FIG. 6 shows the subject of FIG. 5 with the fluidised bed height adjusted to a different value.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fluidised bed drier shown in FIGS. 1 and 2 comprises a drying chamber 1 through which the stream of material to be dried passes over its entire length. At the left-hand end in the drawing the drying chamber 1 is provided with an inlet 2 for the material to be treated, that is to say dried, whereas at its other end, at the right in the drawing, it comprises an outlet 3 for the dried material. The lower part of the drying chamber 1 forms a channel for conveying the stream of material being dried in the form of a fluidised bed. For this purpose the bottom 4 of the drying chamber] consists of a horizontal plate provided with a plurality of fine perforations. Provided under the bottom 4 is a box 5 through which compressed air or gas under pressure is supplied to the perforations of the bottom 4. For this purpose the end 6 of the box 5 situated below the inlet 2 is connected to a conduit 7 for gas or air under pressure.

The gas or air entering the chamber 1 through the perforations in the bottom 4 forms with the particles of material to be dried a fluidised bed which moves over channel of the fluidised bed drier is followed by the bottom 9 of a chute, which bottom 9 is in prolongation of the bottom 4 of the channel. The chute forms a free outflow for the stream of material issuing from the outlet 3, a regulating means being provided capable of varying the friction between the stream of material and the bottom 9 of the chute.

The bottom 9 of the chute is constructed as a perforated plate. Situated below the bottom 9 is an air supply box 8. The flow of air passing out of the air supply box 8 through the perforations of the bottom 9 can be modified.

For this purpose the air supply box 8 can be supplied with air at variable pressure. Two air inlets l and 11 are provided which open into the box 8. The air inlet 10 is connected to the main fan (not shown) of the fluidised bed drier and provided with a throttle valve 12 for regulating the throughflow of air. The air inlet 11 is connected to the box 5 of the fluidised bed drier and provided with a throttle valve 13.

If no air is introduced into the box 8, the material P being dried forms on the bottom 9 of the chute a natural slope which corresponds to the oscillatory conditions of the oscillatory unit 1,5. This slope corresponds to a certain height H of fluidised bed. But if a certain quantity of air is blown through the perforations of the bottom 9, the friction between the material flow P and the bottom 9 of the chute is reduced. Owing to the material flow sliding off more quickly and being aerated, the angle of the slope and with it the height H of the fluidised bed is reduced.

By regulating the throttle valves 12 or 13 the height H of the fluidised bed can be kept to a predetermined desired value.

With the arrangement according to the invention there is no risk of blockages being caused by the formation of lumps from the material particles, since no obstacle is situated in the path of outflow for the stream of material; on the contrary, the height of the fluidised bed is adjusted by varying the outflow process of the stream itself.

Whereas in the embodiment shown in FIGS. 1 and 2 the bottom 9 of the chute follows tangentially the bottom 4 of the channel and is increasingly inclined in the direction of movement of the stream of material, in the embodiment shown in FIG. 3 there is a slight inflection or break between the bottom 9 of the chute and the bottom 4 of the channel. In both embodiments the bottom 9 of the chute is inclined in the direction of movement of said stream at least locally relatively to the horizontal.

In the embodiment shown in FIG. 4, to vary the friction between the stream of material and the bottom of the chute the following measure is adopted. The bottom of the chute is sub-divided in the direction of movement of said stream into two portions 9 and 9 the portion 9 which is downstream in the direction of movement of said stream being capable of being displaced telescopically relatively to the preceding portion 9, so that the length of the chute 9 can be varied. The portion 9 is connected securely to the box 5, whereas the portion 9 can be displaced from the illustrated position into the position indicated by dot-dash lines.

In the extended position of the portion 9 of the chute, a pile of material particles forms thereon which makes the fluidised bed accumulate to a height H. In the retracted position of the portion 9 indicated by dot-dash lines, a smaller pile of material particles forms on the part 9 of the chute and correspondingly the fluidised bed is at a lower height h (also indicated by a dotdash line). By adjusting the portion 9 of the chute, the height of the fluidised bed can be regulated to the desired value.

The embodiment shown in FIGS. 5 and 6 corresponds substantially to the embodiment according to FIGS. 1 and 2. To vary the air flow passing through the perforations of bottom 9, however, there is also provided a shield 14 which can be displaced along the bottom 9. In FIG. 5 the shield 14 is arranged in the direction of movement of the stream of material at the end of the bottom 9, whereby a low height h is obtained for the fluidised bed. In FIG. 6 the shield abuts on the beginning of the bottom 9, resulting in a greater height H for the fluidised bed.

The shield 14 in the embodiment shown in FIGS. 5 and 6 is situated above the bottom 9. But it could also be arranged below the bottom 9, i.e. in the box 8.

To vary the air flow passing through, however, the size of the perforations in the bottom 9 could also be made variable, for example by means of a shield corresponding to the shield 14 and provided with the same perforations as the bottom 9, said shield being displaceable along the bottom 9 by an amount corresponding to half the pitch of the perforations.

In the shown embodiments the chutes do not have any side walls. Of course the chutes can be provided with side walls which, if desired, can have perforations connected to an air source.

The illustrated regulating means for varying the friction between the material stream and the bottom of the chute can be controlled by a sensor arranged above the fluidised bed and adjusted to the desired height of the fluidised bed.

We claim:

1. In a fluidised bed device having a perforated channel for a stream of material travelling through said channel, and a chute for the outflow of said stream, said chute following said channel in the direction of said stream, an arrangement for regulating the height of said stream which is characterized in that the bottom of said chute follows said channel in prolongation of the bottom of said channel, said chute forming a free outlet for said stream, and that a regulating means is provided capable of varying the friction between said stream and said bottom of said chute.

2. Device according to claim 1, in which said bottom of said chute has perforations and, at its lower side, a gas or air supply box for passing a variable flow of gas or air through said perforations.

3. Device according to claim 2, in which said gas or air supply box is adapted to be supplied with gas or air at variable pressure for varying said flow of gas or air.

4. Device according to claim 2, in which the size of said perforations in said bottom of said chute is variable in order to vary said flow of gas or air.

5. Device according to claim 2, in which a shield is provided being displaceable along said bottom of said chute, for varying said flow of gas or air.

6. Device according to claim 1, in which said bottom of said chute is sub-divided, in the direction of said stream, into at least two portions, the downstream one of said portions being capable of being displaced teletangential relationship thereto, said bottom of said chute being inclined to an increasing extent in the direction of said stream.

9. Deviceaccording to claim 1, in which at least a portion of said bottom of 'said chute is tiltable relatively to the horizontal. 

1. In a fluidised bed device having a perforated channel for a stream of material travelling through said channel, and a chute for the outflow of said stream, said chute following said channel in the direction of said stream, an arrangement for regulating the height of said stream which is characterized in that the bottom of said chute follows said channel in prolongation of the bottom of said channel, said chute forming a free outlet for said stream, and that a regulating means is provided capable of varying the friction between said stream and said bottom of said chute.
 2. Device according to claim 1, in which said bottom of said chute has perforations and, at its lower side, a gas or air supply box for passing a variable flow of gas or air through said perforations.
 3. Device according to claim 2, in which said gas or air supply box is adapted to be supplied with gas or air at variable pressure for varying said flow of gas or air.
 4. Device according to claim 2, in which the size of said perforations in said bottom of said chute is variable in order to vary said flow of gas or air.
 5. Device according to claim 2, in which a shield is provided being displaceable along said bottom of said chute, for varying said flow of gas or air.
 6. Device according to claim 1, in which said bottom of said chute is sub-divided, in the direction of said stream, into at least two portions, the downstream one of said portions being capable of being displaced telescopically relatively to the upstream one of said portions, so as to vary the length of said chute.
 7. Device according to claim 1, in which said bottom of said chute is inclined in the direction of said stream at least locally relatively to the horizontal.
 8. Device according to claim 7, in which said bottom of said chute follows said bottom of said channel in a tangential relationship thereto, said bottom of said chute being inclined to an increasing extent in the direction of said stream.
 9. Device according to claim 1, in which at least a portion of said bottom of said chute is tiltable relatively to the horizontal. 